Field of the Invention
This invention relates to optical technologies, and in particular, it relates to light source systems and laser light sources.
Description of the Related Art
In conventional technologies, the light power of a typical single semiconductor laser device is about a few hundred mW, or up to 1-2 W for higher powered ones. It is currently difficult to achieve output power of a few watts or over 10 W for single semiconductor laser devices.
In some applications that require high power semiconductor lasers, such as projector, stage lighting system, etc., where the required light output is a few tens of watts, arrays of semiconductor lasers may be employed. Conventional semiconductor laser arrays simply arrange semiconductor lasers such as laser diodes in two-dimensional arrays, and use collimating lenses to collimate the light from the laser diodes.
FIG. 1a shows a 4×4 laser diode array. Typical light distribution of a laser diode 11 is an elliptical Gaussian distribution, with a relatively large divergence angle. The collimating lens (not shown) is typically a lens with rotational symmetry, which can collimate the light from the laser diode 11.
Also as shown in FIG. 1a, conventional laser diode arrangements are typically a planar arrangement with output light in the normal direction, where each laser diode 11 is mounted on a base 12. The projected area of the base 12 is larger than the area of the corresponding laser diode 11. The inventors of the present invention discovered through research that such a normal planar arrangement has certain disadvantages as follows:
Referring to FIG. 1b, because the output light distribution of the laser diode 11 is an elliptical Gaussian distribution, an elliptical light spot 13 is formed by the collimating lens (not shown in the drawing), and the area of the elliptical light spot 13 is much smaller than the corresponding projected area 14 of the base 12. Because the projected area 14 of the base 12 is larger than the corresponding projected area of the laser diode 11, the density of arrangement of the laser diode 11 cannot be too small; moreover, because the area of the elliptical light spot 13 is much smaller than the corresponding projected area 14 of the base 12, large gaps are formed between the light spots 13 in the array, so that the light spots 13 cannot be densely packed. Therefore, the light power density is impacted by the size of the base 12 and cannot be further increased. As a result, the advantages of high power density of laser cannot be fully realized. Although the light beams can be focused by focusing lenses into one light spot, the focused light beams are no longer parallel but have relatively large divergent angles, which is disadvantageous to the design of downstream optical systems.
To increase light power density, Chinese patent CN101937163 provides a light source unit that can achieve a tight packing of laser light spots. As shown in FIG. 2, the light source unit 200 includes a light source group 210 and a reflector group 220. The light source group 210 includes 6 light sources 201, and each light source 201 is formed by a light emitting device 205 and a collimating lens 207. The reflector group 220 includes 6 parallel reflectors 225 corresponding to the light sources 201, to reflect the light beams from the light sources 201 into light beams having smaller spacing between each other. As shown in FIG. 2, if the diameter of the collimating lens 207 of the light source 201 is a, and the row space between two light sources is b, then the total column length of the light source group 210 with 6 light sources is 6a+5b. Because the light beams from the collimating lenses 207 of the light sources 201 are parallel lights, the light beam from the light source group 210 has a cross-sectional size of 6a+5b in the column direction of the array. If one reflector 220e is used to directly reflect the light beams from the light source group 210 relative to the column direction, the reflected light beam from the reflector 220e will have a cross-sectional size of 6a+5b in its column direction. But, if a rectangular reflector 225 is provided for each row of light sources, and the reflectors are arranged in a way that the spacing between adjacent rectangular reflectors 225 is reduced in the direction of the optical axis of the light source group 210, then the reflected beam from the rectangular reflectors 225 will eliminate the spacing b between the light sources 201 in the light source group 210. Thus, the length of the reflected beam in its column direction becomes 6a, resulting in more tightly packed laser light spots.
By studying the conventional technology, the inventors of this invention discovered that, each group of parallel reflectors can only compress light spot spacing in one direction, and the light spot spacing in the other, perpendicular direction is still large. To obtain a light spot array with compressed spacing in both directions, two groups of reflectors are required, increasing the volume of the light source unit and making it inconvenient in actual products.